Oh my! That emphasizes a weakness is the way they programmed the lot exporting routine. If they wanted to include the feature of exporting an occupied lot, they should have pruned all memories of acquaintances outside the household.

There is one way to prune the memories and it keeps the lot inhabited. Move the lot to the lot bin. But, if you put the lot back in the neighborhood, you end up with no friends etc. I did it once accidently and it took forever to straighten out the family relationships. I don't recommend it.

If you're worried about losing all the items on the lot by a move out, the squinge's bush will let you move out and leave everything in place. The only things I found it doesn't work for are vehicles and the aspiration objects but those can be dropped in a Sim's inventory so you don't lose them.